1. Field of the Invention
The present invention relates to a method for estimating and controlling a polishing profile or polishing amount during a polishing process of flatly polishing a surface of an interconnect material or an insulating film formed on a polishing object, such as a wafer, in manufacturing of a semiconductor device, and a polishing method and a polishing apparatus which employ the above method in performing polishing. The present invention also relates to a program for controlling a polishing apparatus, and a storage medium in which the program and data have been stored.
2. Description of the Related Art
In a CMP process of flatly polishing a surface of an interconnect material or an insulating film laminated on a substrate in manufacturing of a semiconductor device, polishing conditions employed in operation of a manufacturing line are previously optimized, and successive polishing operations of substrates are performed repeatedly under the same optimized polishing conditions until wear of a polishing member reaches its limit. However, in the course of wear of the polishing member, a surface topology of the interconnect material or insulating film on the substrate after polishing, herein referred to as polishing profile, changes with time in accordance with a degree of wear of the polishing member. In general, a change of the polishing member is set at a time before a change in a polishing profile with time begins to affect device performance.
Semiconductor devices are becoming finer these days, and processing speeds of devices are becoming higher by multi-level lamination of interconnects. With such semiconductor devices, a surface topology of an interconnect metal or an insulating film after polishing, i.e., a polishing profile, is required to be made flat with higher accuracy. Thus, an acceptable change in polishing profile with time is narrower for devices with finer and advanced multi-level interconnects. This necessitates more frequent changes of worn polishing members. However, consumable members for use in CMP are generally very costly, and therefore an increase in a frequency of change of consumable members significantly affects device cost.
A method is known conventionally which comprises measuring a thickness of a film on a wafer before and after polishing in a CMP process and, based on results of this measurement, setting polishing conditions for a next wafer to be polished (see, for example, Published Japanese Translation of PCT international Publication No. 2001-501545). According to this technique, a polishing coefficient, indicating a polishing rate per unit surface pressure, is determined as an average value without a distribution on a wafer based on results of measurement, and such polishing time and polishing pressure for the next wafer are set that will provide a desired average polishing amount. This is because the polishing coefficient changes with condition of polishing (including wear of consumable member, a condition of slurry, temperature, and the like), and therefore it is necessary to update the polishing coefficient, and thus polishing time and polishing pressure as needed, by using the results of measurement. However, techniques for detecting an end point of polishing are fully developed nowadays, and it is now possible to automatically terminate polishing when a desired film thickness has been reached despite a change in a state of polishing. Accordingly, it is not necessary now to employ the above-described technique.
Further, since this conventional technique merely updates the polishing time and polishing pressure so that a desired average polishing amount can be obtained, it is not possible to correct a change in the polishing profile with time due to wear of a polishing member.
Another known technique involves monitoring and calculating a thickness of a remaining film during polishing in a CMP process, and changing each of pressures of pressure chambers so as to enhance flatness of the remaining film, thereby correcting a change in a polishing profile with time due to a change with time in slurry or polishing pad used (see, for example, Japanese Patent Laid-Open Publication No. 2001-60572). This technique is intended to be applied to a wafer polishing process in which a thickness of a film is measured with an optical sensor. A number of measurement points is inevitably limited by a spot size of the optical sensor and a rotational speed of a polishing table. This technique thus has a problem in that sufficient information cannot be obtained for setting chamber pressures that are to be changed to flatten the remaining film after polishing. Further, when this technique is applied to a wafer polishing process employing a high polishing rate, there is a case in which a response time from measurement of thickness of a remaining film until feedback of a corrected value is longer than the time until termination of polishing. Thus, the polishing can be terminated before control achieves flattening of the remaining film.